Nonwoven liner material and method of making same



Aug. 11, 1970 N. s. NEWMAN ErAL 3,523,861

NQNWOVEN L INER MATERIAL AND METHOD OF MAKING SAME.

Filed Dec. 20, 1966 FIG 2 United States Patent Office 3,523,861 PatentedAug. 11, 1970 3,523,861 NONWOVEN LINER MATERIAL AND METHOD OF MAKINGSAME Nicholas S. Newman, West Newton, Mass., assignor to The KendallCompany, Boston, Mass., a corporation of Massachusetts Filed Dec. 20,1966, Ser. No. 603,226 Int. Cl. D04h N58 US. Cl. 161-151 8 ClaimsABSTRACT OF THE DISCLOSURE An unspun and unwoven array of textile-lengthfibers or blend of such fibers is lightly needled until a portion of thefibers have been reoriented into closer mechanical engagement with eachother. This array of fibers is brought into contact, under heat andpressure, with the surface of a transiently thermoplastic film capableof becoming thermoset when heated, adhesive being effected along only aportion of the lengths of the fibers.

This invention relates to nonwoven fabrics, and more particularly tononwoven lining or interlining material comprising a needled array oftextile-length fibers bonded to a conformable film.

Textile fibers as delivered by a card, garnett, or air-lay machine arecustomarily arrayed in a web or fleece wherein the thickness of thefleece is only a fraction of the fiber length, so that the principalfiber axis lies in a more or less horizontal plane. The fibers may bepredominantly parallelized or randomly oriented within that horizontalplane.

Various methods of unifying such fibrous arrays, to form nonwovenfabrics, are practiced, the most common being that of impregnating thearray with a polymeric binder to form a so-called bonded nonwovenfabric. Such products have a wide utility in the industrial and consumerproduct fields, but due to certain deficiencies in pliability andconformability, coupled with their undesirable high density and lack ofloft or insulating value, bonded nonwoven fabrics have not found wideacceptance in the field of liners or interliners for garments.

In order to provide nonwoven fabrics which are soft and felt-like,therefore, it is common practice to subject fibrous arrays to a needlingoperation, as in a needle loom, whereby barbed needles descendingperpendicularly to the principal plane of the fibers will grasp acertain proportion of the fibers and forcibly reorient them in adirection more or less normal to their original horizontal orientation.The affected fibers are packed together into aggregated configurationswhich have been called ligations. This operation lends a degree ofstrength to the fibrous array, while maintaining loft and softness ifthe needling operation is not too severe.

The strength thus provided, however, is due to a purely mechanicalentanglement of the fibers. Since the majority of the fibers in alightly-needled fleece are either unaffected or only slightly affectedby the needling, lightlyneedled fleeces have low abrasion resistance,and shed fibers rather readily when subjected to friction. If attemptsare made to overcome this by repeated needlings, it is found thatincreased fiber anchorage is indeed attained, but at the expense ofincreased compactness and density of the fabric, and decreasedconformability, softness, and insulating value.

Other expedients which have been resorted to in order to achieve betterfiber anchorage include back-coating the needled fleece with a binder:flash-heating certain fibrous arrays to effect thermal bonding; andspraying the fleece with a solvent or with a latent solvent which issubsequently activated. All such expedients have undesirable aspects ofeither wet processing and the need for drying; possible fire hazard; orthe known hazards of solvent spraying. It is with improvements in theart of producing soft, conformable, needled nonwoven fabrics, suitablefor interlinings, that the present invention is concerned, and a methodof producing such nonwoven fabrics is the primary object of theinvention.

It is also an object of this invention to provide a method of treating aneedled nonwoven fabric so that its tensile strength is increased, whileits elongation is decreased without a substantial decrease inconformability.

It is a further object of the invention to provide a needled nonwovenfabric which can be napped without destruction or excessive fiber loss.

Other objects of the invention will be more readily understood from thefollowing description and drawing, in which FIG. 1 represents anapparatus suitable for carrying out the process of this invention FIG. 2is an enlarged cross-sectional view of a product of this invention.

The present invention comprises the steps of:

(1) Forming a fleece or batt of textile-length fibers on afiber-arranging device.

(2) Lightly needling the fibrous array in a needle-loom.

(3) Bringing the needled fibrous array into face-to-face contact withone surface of a transiently thermoplastic film while the surface ofsaid film is in an adhesive condition.

(4) Combining the needled fibrous array with the film by means of heatand pressure.

(5) Post-heating the assembly to convert the film to a thermosetcondition.

By textile-length fibers is meant those which are long enough to behandled satisfactorily on dry-process fiberassembling textile machines,such as cards, garnetts, air-lay machines and the like. In general, theaverage fiber length is one-half inch or greater. The particular type offiber used will depend on the use to which the nonwoven fabric is put,and on economics. Cotton, wool, rayon, polyamide, polyester,polyacrylic, and modified acrylic fibers, or blends thereof are suitablefibers of choice. When synthetic fibers are used, it is frequentlyconvenient to use a blend of fibers of different deniers, to get acombination of high cover factor and high loft.

The needling operation is conventional, as in a Hunter Needle Loom, andneeds no further description here except to indicate that for maximuminsulating and cushioning value, the preferred products of thisinvention are subjected to not more than to 300 needlings per squareinch.

The particular types of film with which the needled fibrous array isbrought into contact are those which have a temperature range withinwhich they are tacky and adhesive, but which contain cross-linkingreactants so that on heating or curing at elevated temperatures, thefilm becomes irreversibly set and cannot be reverted to a plasticcondition. Such films at room temperature or somewhat above partake ofthe natureof thermoplastic films, and will for convenience be calledherein transiently thermoplastic.

One type of such films particularly useful in the practice of thisinvention is a modified acrylic film supplied by Rohm and Haas under thetrademark Oroform. This film is tacky and plastic at room temperature,flowing readily under modest heat and pressure. If heated to 300 F. orhigher, the film cross-links internally and becomes thermoset.Subsequent to such a heat-setting or curing process, the film is quitethermostable, withstanding prolonged exposure to temperatures of 300 F.and over. It will yellow slightly in one minute at 400 F., but does notmelt or decompose to an adverse degree even at higher temperatures.

For a description of a suitable process for producing the products ofthis invention, reference is made to FIG. 1, wherein a' supply oftransiently thermoplastic film 10 is drawn from a supply roll 12, saidfilm being mounted on a backing of release paper 13. The release paperis desirable due to the soft and somewhat adhesive nature of films ofthis type: its use is well known to those skilled in the film art andwill not be elaborated upon here. From the supply roll the film upon itsrelease paper passes to the nip formed by a pair of calender rolls,heated, one roll conveniently being of steel or other metal and theother of a resilient composition such as fiber or husk. At the nip, thesemi-adhesive film is combined with a lightly needled nonwoven fabric14, from a conventional supply roll 16.

At the calender nip the needled nonwoven fabric and the semi-adhesivefilm are forced by pressure into intimate contact, as explained morefully in connection with FIG. 2. If the temperature in the calenderrolls is 400 F. or over and the contact time is prolonged, theconversion of the film from a thermoplastic to a thermoset condition mayoccur in the calendering operation. For speed in processing, however, itis preferred to have the calender operate at 300-350 R, which unites thefilm and the needled web, and to effect the conversion of the film to athermoset condition in a subsequent heating stage 22, which may be aheated oven, a bank of infra-red lamps, or the like. From this curingstage the film-fabric combination passes to a wind-up roll 26, while therelease paper, separating from the film at the calender nip, isrecovered at the wind-up roll 24.

A typical product of the invention is shown considerably enlarged atFIG. 2, wherein a lightly-needled nonwoven fabric 40 is shown adheringto a now-thermoset film 42. It is characteristic of the economies ofthis invention that although the film layer in the final product is notthermoplastic or temperature-sensitive, during the combining operationno added adhesive layer on the film is necessary to secure asatisfactory bond between fibers and film.

The internal resistance to delamination, which manifests itself inminimal fiber shedding, is a result in part of the fact that needledtufts of fibers or ligations, 44, are firmly embedded in the filmsubstance at their lower extremities. An even more significant factor,however, is that a substantial number of the fibers which have escapedbeing engaged in the needling process, as at 46, have been pressed downonto the surface of the film during the calendaring operation and havebecome firmly adherent thereto along a portion of their length. Thefibers are therefore not only mechanically engaged at intervals byneedling, but a large proportion of them are adhesively bonded to thebase film, and therefore resist abrasion.

- One specific embodiment of the present invention is illustrated in thefollowing example.

EXAMPLE I By means of a cross-lay device, a fibrous fleece was preparedfrom 1.5 inch long acrylic fibers, 50% 3 denier, 40% 5 denier, and 8denier. The fleece was lightly needled in a Hunter needle loom at a rateof 260 needle penetrations per square inch. The original weight of thefleece, 180 grams per square yard, dropped to 140 grams per square yardin the needling process.

In an apparatus arrangement similar to that of FIG. 1, the needledfleece was superimposed up on a breathable, tacky Oroform C-16 film,supported on release paper. The laminar combination was then passedthrough a nip formed by a fiber-filled roll and a steel roll heated to280 F., at a pressure of 1,000 pounds per inch of nip width (totaljournal ram pressure divided by width of nip). The film portion of thelaminate was then cured to a thermoset condition by heating thecombination to 320 F. for one minute in an oven.

The interaction between film and fabric is shown by the followingphysical constants:

Tensile strength, lbs. Elongation, percent The thickness of the finalproduct was about A inch, and the apparent density of the nonwovenportion (weight divided by unloaded volume) was 0.11 grams per cubiccentimeter, compared with an absolute density for acrylic fibers of 1.17grams per cubic centimeter.

As mentionedabove, theproducts of this inventionare suitable for use asgarment liners, on account of their insulating value. The insulatingvalue of a liner material is related to the free air spaces between thefibers, and is therefore inversely proportional to the density of thefibrous mass. In the preferred embodiments of this invention, thecombined effects of needling and adhesive bonding are such that 'the'unloaded fibrous product has an apparent density not greater than 20% ofthe absolute density of the substance. Thus, for viscose rayon fiberswith an absolute density of about 1.5 grams per cubic centimeter, thedensity of the final product is preferably not more than 0.3 grams percubic centimeter. It is difficult, if not impossible, to maintain such alow fiber density either by needling or film-bonding alone, andsimultaneously maintain adequate tensile strength.

The unexpected interaction between film and fiber is also shown byconsidering the way in which each suppresses the elongation of theother. Both the film and the nonwoven fabric had an elongation at breakin the machine direction of over which indicates a lack of stability andretention of shape for lining purposes. By embedding a substantialportion of the fibers into the surface of the film substance by theprocess of this invention, the elongation at break of the combination isonly a small fraction of the elongation of the separate components, andthe enhanced stability of the product makes it suitable for use as agarment liner.

The degree of embedment of the fibers of the nonwoven fabric is attestedby the fact that the product of Example I can be napped on commercialnapping equipment, doubling its apparent thickness, withoutobjectionable fiber loss or damage to the integrity of the structure.

In the preferred products of my invention, the bonding of the fibers tothe film is effected solely by film substance, but minor amounts ofadded binder may be used without substantially detracting from theutility of the products.

Having thus described my invention, I claim: 1. A soft, conformablenonwoven fabric suitable for garment lining purposes which comprises:

an unspun and unwoven array of textile-length fibers in combination witha thermoset film,

a portion only of said fibers being needled into mechanical engagementwith each other by subjecting said fibers to not more than to 300 needlepunches per square inch,

certain fibers from said portion as well as certain of the other fibersbeing adhesively bonded to the surface of said thermoset film along aportion only of their lengths,

the adhesive bonding of said fibers being derived essentially from saidfilm substance.

2. The product according to claim 1 in which the fibers are distributedisotropically. 3. The product according to claim 1 in which the fiberscomprise a blend of man-made fibers of different deniers.

4. The product according to claim 1 in which the density of the fibrousportion of the product is not greater than one-fifth of the absolutedensity of thefibers.

5. The product according to claim 1 in which the thermoset filmcomprises a cross-linked acrylic polymer.

6. The process of making a soft, conformable nonwoven fabric suitablefor garment lining purposes which comprises forming an unspun andunwoven array of textile-length fibers.

lightly needling said fibrous array by subjecting said fibers to notmore than 150 to 300 needle punches per square inch,

superimposing said array on a transiently thermoplastic film capable ofbecoming thermoset on heating,

and uniting along a portion only of their lengths a substantial portionof said fibers to the surface of said film by heat and pressure.

7. The process of claim 6 in which the extent of the needling operationis not over 300 penetrations per square inch.

8. The process according to claim 6 in which the film is across-linkable acrylic film with a tacky, adhesive surface at roomtemperature,

said film being capable of becoming non-tacky and heat-set at elevatedtemperatures.

References Cited UNITED STATES PATENTS 3,206,351 9/1965 Smith 161803,282,771 11/1966 Goodman et a1 161151 3,348,992 10/ 1967 Cochran 16166OTHER REFERENCES Union Carbide Technical Int., UCAR Latex 893, June,1966 (Class 161Acrylic Resin Digest).

ROBERT F. BURNETT, Primary Examiner R. L. MAY, Assistant Examiner US.Cl. X.R. 156-148, 306

